1. Field of the Invention
The field of invention relates to a submersible pump system and a method its use. More specifically, the field of invention relates to a system for and a method of accessing a well bore production zone while the system is in use.
2. Description of the Related Art
One method of producing hydrocarbon fluid from a well bore that lacks sufficient internal pressure for natural production is to utilize a submersible pumping device. A string of tubing or pipe known as a production string suspends the submersible pumping device near the bottom of the well bore proximate to the producing formation. The submersible pumping device is operable to retrieve production zone fluid, impart a higher pressure into the fluid and discharge the pressurized production zone fluid into production tubing. Pressurized well bore fluid rises towards the surface motivated by difference in pressure.
A submersible pump system is installed during completion operations in a specifically designed well bore production zone. The production zone is a portion of the well bore in-between or below a packer or plug where hydrocarbons are produced for production. The packers and plugs isolate the portion of the well bore that is in fluid communication with the hydrocarbon-bearing formation from the remainder of the well bore. Fluid isolation of the production zone permits access, maintenance and even fluid isolation of the remainder of the well bore without disturbing the production zone.
Accessing the production zone for maintenance or information gathering after installing plugs or packers is typically avoided because it is expensive, time consuming and a technically challenging endeavor. Reasons for accessing the production zone include making additional production perforations in the well bore casing, treating the hydrocarbon-bearing formation with chemicals to alter its production profile, including applying acid treatments or removing scale, and performing routine and specialized production logging with coiled tubing or wire line tools, including identifying zones of water and oil.
Known techniques for using a submersible pump system while also accessing the production zone create significant operational problems. Although installing a submersible pumping device in a production zone is relatively easy, accessing the production zone through the submersible pumping device is difficult if not impossible. Submersible pumping devices do not provide direct mechanical access into the production zone from the production tubing string because the pump obstructs access except for fluids passing via the pump impellers.
A Y-tool can offer access through a submersible pump system. The Y-tool requires the use of a “blank plug” while the submersible pumping device is in use to access the production zone. A blank plug set in the bypass pathway prohibits fluid from recycling from the submersible pumping device discharge back into the well bore through the bypass branch of the Y-tool. Wire line operations for setting and removing blank plugs are expensive, pose operational and personnel safety concerns and usually results in deferred production.
A Y-tool with an internal flapper or diverter, sometimes called an “auto Y-tool”, poses significant downtime risk if it mechanically fails. Manufacturers do not design auto Y-tools for removal during service, so if a mechanical problems with the flapper represent catastrophic failure of the device and a system-wide issue. Repair or replacement of the auto Y-tool requires installation of a work over rig and removal of the entire production tubing string. A replacement operation can take from 10 to 30 days to plan and execute, resulting in costly downtime. In addition, auto Y-tools require that the operator turn the submersible pumping device on and off to manipulate the flapper position for accessing the production zone. Repeated use can lead to wear and tear on both pump and flapper device, shortening its operational life span.